Classicly

Mary Roberts Rinehart -- "America's Agatha Christie," as she used to be called -- set this story in a New York suburban town, shortly after the end of the first world war. Dick Livingstone is a young, successful doctor, who in the course of events becomes engaged to Elizabeth Wheeler. But there is a mystery about his past, and he thinks himself honor-bound to unravel it before giving himself to her in marriage. In particular, a shock of undetermined origin has wiped out his memory prior to roughly the last decade.